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Ins and outs of feeding tubes (Proceedings)

Addressing the nutritional needs of our hospitalized and critical care patients can dramatically improve their outcomes, but also allows them to return home sooner. Oral enteral nutrition is the ideal route, but if the patient is unable or unwilling to consume at least 85% of their calculated resting energy requirements (RER) than another route needs to be utilized.

Nasoesophageal/Nasogastric tube placement

When oral nutrition is not an option, what other options are available? There are a number of feeding tube options available, the choice of tube will be dependent on the condition of the patient, the disease being addressed, and expense of administration, availability of intensive care facilities, the preferred food and anticipated length of feeding assistance.

The first step would be to calculate the RER for the individual patient. The most widely used formula is: (weight in kilograms X 30) + 70 = RER. This formula can be utilized in both cats can dogs over 2 kilograms to 45 kilograms. (1, 2, 3) Alternately, for cats you can use: (weight in kilograms × 40) = RER. For animals that are below 2 kilograms or above 45 kilograms the logarithmic formula can be used: (weight in kilograms × 70)0.75

The best feeding tubes for prolonged use are made of polyurethane or silicone. For short term feeding, usually less than 10 days, polyvinylchloride (PVC) tubes can be used. These are not appropriate for long term feeding because they tend to become stiff with prolonged use causing additional discomfort for the patient. Silicone is softer and more flexible than other tube materials and has a greater tendency to stretch and collapse. Polyurethane is stronger than silicone, allowing for thinner tube walls and a greater internal diameter, despite the same French size. Both the silicone and polyurethane tubes do not disintegrate or become brittle in situ, providing a longer tube life. The French unit measures the outer lumen diameter of a tube and is equal to 0.33 mm.

While force feeding can be used to provide the necessary nutrition, this is usually too stressful to the patient, not to mention the stress to the owner. Seldom is this method able to deliver the volume of nutrients necessary to meet the patients' needs on a regular basis.

Nasoesophageal tubes are useful for providing short term nutritional support, usually less than 10 days. They can be used in patients with a functional esophagus, stomach and intestines. Nasoesophageal tubes are contraindicated in patients that are vomiting, comatose or lack a gag reflex.

The length of tube to be inserted is determined by measuring from the nasal planum along the side of the patient to the caudal margin of the last rib. This indicates the ideal tube placement-mark this area with either a piece of tape or permanent marker. After instilling a few drops of the lidocaine into the nose and waiting 10-15 minutes for full analgesic effect, a sterile catheter of sufficient length (8 Fr × 42 inch in dogs > 15 kg, 5 Fr × 36 inch in dogs < 15 kg) is advanced into the nose. The tube should be passed with the tip directed in a caudoventral, medial direction into the ventrolateral aspect of the external nares. The head should be held in a normal static position. As soon as the tip of the catheter reaches the medial septum at the floor of the nasal cavity in dogs, the external nares are pushed dorsally, this opens the ventral meatus, ensuring passage of the tube into the oropharynx. In cats, the tube can be inserted initially in a ventromedial direction and continued directly into the oropharynx. The tube is inserted until the tape tab or marked area is reached. To evaluate proper tube placement, 3-15 ml or sterile water or saline can be injected through the tube and the animal evaluated for coughing. Coughing would indicate the tube is placed in the lungs not the esophagus. Lateral radiographs may also be taken to confirm tube location. After confirmation of position, the tube is secured with either glue or sutures at the external nares and along the dorsal midline along the bridge of the nose. Continue to direct the tube over the head and secure with a bandage around the neck. Place the catheter plug into the catheter. An Elizabethan collar is used in most animals to prevent inadvertent removal of the tube.

Complications include epistaxis, lack of tolerance of the procedure, and inadvertent/ intentional removal by the patient. These tubes should not be used in vomiting patients or those with respiratory disease.

To place a nasogastric tube, follow the same procedure, but measure the length to 3-4" past the last rib. Nasogastric tubes increase the risk of gastroesphageal reflux increasing the incidence of esophageal strictures. This is due to passage through the cardiac sphincter of the stomach allowing reflux of gastric acids into the esophagus.

Due to the small internal diameter of these tubes, only liquid enteral diets can be used. They can either be fed through a syringe pump as a continuous rate infusion or bolus fed. If feeding through a syringe pump, completely change the delivery equipment every 24 hours to help prevent bacterial growth within the system. Tube clogging is a common problem; a syringe pump may help to decrease the incidence as will flushing well before and after bolus feeding. If the tube becomes clogged, replacement may be necessary. Diluting the liquid with water may also help, though this further decreases the caloric concentration of the diet, increasing the volume necessary to meet the caloric needs.

When removing, the tube may be simply pulled out after the glue or sutures are removed.